My max pop city so far is just shy of 100,000. I’d say the average is closer to 25. Frames drop when you scale across the map when you’re quite zoomed out, but not for more than a half second. It’s not the kind of game where I move the camera much - I tend to obsess over certain districts and niche building strategies lmao.
I believe I had to manually change it. I’ve added a lot of mods as well - this can cause some instabilities but I’ve found a happy balance. I average 25-30 frames on medium settings but as the game isn’t anything fast paced this works well for me.